Train services have been cancelled or cut due to heat as people are advised to only travel if necessary.

London Northwestern Railway has cancelled all services on the Abbey Line and greatly reduced other services from Watford Junction after the Met Office issued its first ever red warning for high heat.

LNR and TFL advise travelling only when essential during the heatwave (July 18 - July 19).

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Due to speed resrictions, there will only be 2 LNR trains per hour calling at most stations between Northampton and London Euston, including Watford Junction.

Network Rail says that rails could buckle, and extreme heat may cause problems with overhead line equipment, which powers some trains.

TFL Chief operating officer Andy Lord said: “If customers do need to travel, they should check before they travel as we are expecting there to be some impact to Tube and rail services as a result of temporary speed restrictions, we will need to introduce to keep everyone safe."

Watford Observer: Weather warnings Graphic: PAWeather warnings Graphic: PA Travellers are advised to carry water.

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